The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical modern multiple speed automatic transmission includes a combination of planetary gear assemblies and selectively engaged clutches which achieve a plurality of forward speeds or gears ratios and reverse.
Whereas three and four speed automatic transmissions were once commonplace, considered suitable and provided sufficient flexibility and performance, the industry and consumer preference is moving to six, seven and eight speed automatic transmissions.
In such transmissions, various elements of a plurality of planetary gear assemblies are connected by permanent couplings, selectively connected by clutches and selectively grounded by brakes. Specific combinations of the clutches and brakes are engaged or activated to provide a sequence of numerically related gear ratios and thus speed and torque ratios.
Because they so closely match the power and torque curves of the engine to the imposed load and speed of the vehicle, such six, seven and eight speed transmissions provide significant performance enhancements and reduced fuel consumption.
The present invention is directed to an eight speed automatic transmission having a good ratio progression, excellent gear mesh efficiency, low spin losses and low pinion speeds.